Stability and activity of an Enterobacter aerogenes-specific bacteriophage under simulated gastro-intestinal conditions

Abstract

A bacteriophage, designated UZ1 and showing lytic activity against a clinically important strain (BE1) of Enterobacter aerogenes was isolated from hospital sewage. The stability and lytic activity against this strain under simulated gastro-intestinal conditions was evaluated. After addition of bacteriophage UZ1 to a liquid feed at gastric pH 2, the phage was immediately inactivated and could not be recovered. However, by use of an antacid to neutralize stomach acidity, no significant changes in phage titer were observed after 2 h incubation at 37°C. After supplementing pancreatic juice and further incubation for 4 h, the phage titer remained stable. The persistence of UZ1 in a mixed microbial ecosystem that was representative for the large intestine was monitored using an in vitro simulation of the human intestinal microbial ecosystem. A pulse administration of bacteriophage UZ1 at a concentration of 10 5 plaque-forming units (PFU)/ml to reactor 3 (which simulates the ascending colon) showed that, in the absence of the host, bacteriophage UZ1 persisted for 13 days in the simulated colon, while the theoretical washout was calculated at 16 days. To assess its lytic activity in an intestinal microbial ecosystem, a green fluorescent protein (gfp)-labeled E. aerogenes BE1 strain was constructed and gfp-specific primers were designed in order to quantify the host strain using real-time PCR. It was observed that bacteriophage UZ1 was able to replicate and showed lytic activity against E. aerogenes BE1/gfp in an intestinal microbial ecosystem. Indeed, after 17 h a 2 log unit reduction of E. aerogenes BE1/gfp was measured as compared with the assay without bacteriophage UZ1, while the phage titer increased by 2 log units at an initial multiplicity of infection of 0.07 PFU/colonyforming unit. This is the first report of an in vitro model to study bacteriophage activity in the complex intestinal microbial community.

Biogenic Silver for Disinfection of Water Contaminated with Viruses

“…The bacteriophage UZ1 was obtained from a phage stock made by Verthé et al (38). To detect phages, the soft agar layer method described by Adams (1) was applied, using serial 10-fold dilutions of the samples in SM medium (6 (38).…”

“…This DNA phage, a T7-like coliphage of the genus Podovirida (order Caudovirales) (38), is infective for Enterobacter aerogenes BE1, a species belonging to the normal digestive microbiota (30). The virucidal action of biogenic Ag 0 was evaluated in drinking water and compared with the use of ionic Ag ϩ and chemically produced nAg 0 .…”

The potential role of endogenous bacteriophages in controlling invading pathogens

“…Coliphages and Enterobacter phages are resistant to acid up to pH 3; at pH 2.5 and lower their activity rapidly diminishes. Therefore, diet rich in alkali (milk) and other foodstuffs neutralizing gastric acid may have phage-protective effects, and it is thus believed that phages should be given with a meal or with alkali [12,35]. Moreover, infection of E. coli by phages can be inhibited by the presence of certain bile salts and carbohydrates [36], so a diet influencing these parameters may also alter the activity of intestinal phages.…”

Survival and Metabolic Activity of Pediocin Producer Pediococcus acidilactici UL5: Its Impact on Intestinal Microbiota and Listeria monocytogenes in a Model of the Human Terminal Ileum

“…From an initial concentration of 5.74 and 6.57 log 10 cfu mL −1 , concentrations of 3.57±0.67 and 4.15±0.53 log 10 cfu mL −1 were obtained, respectively, for Bac + and Bac − after 8 h. Reductions thus ranged from 1.3 to 2.8 log 10 cfu mL −1 depending on the strain and concentration added compared with the theoretical washout. It was determined for an inert particle by Verthé et al [47] corresponding to a reduction of 0.87 log 10 cfu mL −1 after 8 h. Regardless of the initial concentration, the Pediococcus population seemed to stabilize between 3.5 and 4.5 log 10 cfu mL −1 after 8 h of fermentation. Finally, all the cells identified as P. acidilactici UL5 recovered from the fermentation medium on days 24 and 31 were still able to inhibit L. ivanovii HPB 28, based on the agar diffusion test.…”